Field of the Invention
This invention grew out of a need for a connection method for a wire reinforced, extruded PVC product intended to duplicate the function of steel grid. The traditional method for connecting steel grid elements at intersections is to attach a separate piece containing the locking configuration to each end of the structure using a staking approach. This addition of a separate device requires that the locking portion of each end are offset to allow the center line of the grid to pass between the mating pieces. The product herein is made from extruded PVC which is not well suited to providing the required offset. Additionally, the use of a riveting process would not provide adequate strength between the plastic and the steel clip. Another traditional method for connecting steel grid elements is to form the locking configuration into the ends during the pressing operation of their manufacture. Again, the approach is well suited for steel but not for extruded PVC.
A less common method to connect the grid elements is the use of a hook end detail. This approach provides a hook on either end which allows mating pieces to pass through a main beam and connect in an over and under fashion. The need for the offset is eliminated as is the necessity for locating and attaching a separate piece. However, the two cross tees must each slide into their respective slot and then drop into place. The product herein with the dimensional face requires coping at each cross tee end and the connecting method must allow the opposing tee's to move only horizontally as they enter and lock into the main tee. This does not happen with the hook end detail.
U.S. Pat. No. 3,093,221 describes a method which uses a straight-in approach for the cross tees. However, it requires a separate metal clip which locks onto the cross tee ends. The connection means described herein requires no separate piece.
U.S. Pat. No. 4,548,013 describes a version of the hook end detail made using extruded aluminum. This approach does not require a separate clip but is not suitable for the straight-in approach required for a dimensionally decorated and coped design.